The present invention relates to an arrangement comprising a pipe and tubing lining same, and a method of producing this arrangement. The main field of application is in pipelines in which a fluid, e.g. natural gas, is transported under high pressure.
There is a known method of introducing externally coated tubing for lining a pipe with an aperture at the beginning of the pipe by inversion into this pipe, the external surface of the tubing being inverted and glued to the inner wall of the pipe to be lined. The tubing can however also be introduced into a pipe by being pulled in (without being inverted) and then glued.
The types of tubing previously used for this purpose consist mainly of a the coating. Thus pores, which are located in the adhesive itself or within the textile structure which is not completely saturated with adhesive, have the same pressure applied to them as prevails in the lined pipe.
As long as the operating pressure is maintained, as a result of the balance of pressures no damage is to be expected, but some will probably occur with a sudden drop in pressure, e.g. where there is an accident to the pipe or some other operational failures, but even also at times when the pipe is taken out of service as planned. In this case, the complete operating pressure continues to be found in the pores described previously, since this pressure cannot suddenly escape via the coating towards the centre of the pipe, i.e. the flow area of the fluid to be transported with the pipe. Whilst in the region between the inner pipe wall and the coating, the operating pressure of the superpressure pipe continues to be maintained, in the flow area there is e.g. only atmospheric pressure. As a result of this just low counter pressure, there are then expansion processes of the gases trapped in the pores, which are connected with bursting of the tubing (formation of bulges) or even complete tearing of the tubing sheath from the pipe wall.
From BE 886 312 A is already known tubing for transporting hot liquids, especially hot water. In order to prevent damage to the tubing material, in particular an increase in permeability by the hot liquids during operation, the interior of the tubing is lined with an aluminium layer which is impermeable to the liquids.
The object underlying the present invention is to make available an arrangement comprising a pipe and tubing lining same and a corresponding manufacturing method, in which when there is a drop in pressure in the flow area, damage to the lining and the safety and cost risks connected therewith do not arise.
This object is accomplished in relation to the arrangement by patent claim 1 and in relation to the manufacturing method by patent claim 19.
Because there is associated with the tubing blank a barrier layer which has a permeation of less than 1 ml/(bar d m2) for nonpolar gaseous substances and a permeation of less than 0.1 ml/(bar d m2) for polar gaseous substances (d=day), the penetration of the tubing by gases is prevented from the beginning or the diffusion of gases into the space between the pipe inner wall and the flow area is slowed down in such a way that even after many years in continuous service, e.g. 50 years, a sudden drop in pressure in the interior of the tubing would not cause any damage to the lining.
Advantageous developments of the present invention are given in the dependent patent claims.
A barrier layer is preferred in which the permeation of nonpolar and polar gaseous substances is in the range between 0.0001 ml/(bar d m2) and 0.01 ml/(bar d m2).
A particularly advantageous embodiment of the tubing provides for it to be realised as a tubing composite, i.e. multilayer, one layer being configured as the barrier layer. This makes it possible for conventional woven hoses, which have been otherwise coated according to prior art in an extruder with thermoplastic plastics materials and have an inadequate diffusion resistance, also to continue to be used for the tubing. The partitioning effect of the tubing is caused in this embodiment merely by the barrier layer.
The barrier layer consists advantageously of metal, especially aluminium, titanium, copper, iron, zinc, nickel, lead, chromium or iron-zinc and lead-tin alloys. The barrier layer preferably has a thickness of between 10 and 100 xcexcm.
Other suitable materials for the barrier layer are organic substances such as polyvinyl alcohols (PVA) and copolymers of same, liquid crystal polymers (LCP), polyamides (PA), polyacrylonitrile, polyvinylidene-chloride (PVDC), epoxy resins (EP) or organosilicon compounds and inorganic substances such as silicon oxide (SiOx with x=2) or aluminium oxide (Al2O3). It is even possible, in order to reduce the gas permeation, to produce a barrier layer, applied possibly by extrusion, from a thermoplastic plastics material which is intermixed with aluminium particles.
To protect the barrier layer against abrasion or detachment, it can be provided on its radially inner side with a protective layer which is applied for example by extrusion or by dip coating. Suitable as materials for such a protective layer, for gas pipelines and in some cases for high-pressure waste water pipelines, are in particular polyurethane, especially in its realisation as thermoplastic polyurethane elastomer (TPU) and polyester, especially in its realisation as thermoplastic polyether ester elastomer (TPE), and for drinking water, service water, long-distance heating and in some cases high-pressure waste water pipelines, polyolefins including polyethylene (PE) and copolymers of ethylene and other xcex1-olefins and thermoplastic polyolefin elastomers (TPO), thermoplastic styrene-butadiene or styrene-ethylene-propylene copolymers (TPS) and mi inner surface is wrapped.
A further advantageous development of the manufacturing method provides for a tubing blank, possibly an uncoated woven hose according to prior art, to be drawn over a tubular sheath with low gas permeation and forming a barrier layer, or be pulled into same. If the tubing blank is drawn over the tubular sheath, formed for example from aluminium foil, the tubing thus produced can be pulled into a pipe. If on the other hand the tubing is to be introduced into the pipe by an inversion method, it is advantageous to pull the tubing blank into the tubular sheath, possibly formed from aluminium foil or some other material with low gas permeation.
Yet a further advantageous embodiment provides for first of all the pipe to be lined with a tubing blank, having a gas permeation of more than 1 ml/(bar d m2) for polar and nonpolar gaseous substances, and thereafter for the barrier layer to be applied to the inner surface of the tubing blank. By this means, the tubing is only completed during the lining process, such that prior assembly of the tubing is not necessary but just takes place on the building site. The tubing blank must however not exceed a specific gas permeation since possibly for the inversion and gluing to the inner pipe wall under the action of pressure, a minimum impermeability of the tubing blank is necessary.
In this connection it is particularly advantageous if the barrier layer is sprayed on in a liquid state.
This method makes it possible to adjust the thickness of the barrier layer in a cost-optimising manner to the respective nominal operating pressure in the pipe and to a desired service life of the pipe lining.
Further advantageous embodiments are given in the remaining subordinate claims.